Downhole cleaning system

ABSTRACT

The present invention relates to a downhole cleaning system for cleaning an element inside a casing in a wellbore comprising well fluid having a wellbore pressure, comprising the casing, a cleaning tool having a longitudinal direction and comprising a rotatable nozzle head having a plurality of nozzles, a tool housing having an inlet being in fluid communication with the nozzles for jetting well fluid into the tool, a flow hindering element arranged on an outside of the housing dividing the tool in a first and a second tool part and dividing the casing in a first and a second casing part and a rotatable shaft connecting the nozzle head with the housing, wherein the system further comprises a pumping device for pressurising the well fluid in the first part of the casing to a pressure substantially above the wellbore pressure and above a pressure in the second part of the casing so that well fluid is pumped in through the inlet and out through the nozzles. Furthermore, the invention relates to a wireline cleaning tool and to a cleaning method.

FIELD OF THE INVENTION

The present invention relates to a downhole cleaning system for cleaningan element inside a casing in a wellbore comprising well fluid having awellbore pressure, comprising the casing, a cleaning tool having alongitudinal direction and comprising a rotatable nozzle head having aplurality of nozzles, a tool housing having an inlet being in fluidcommunication with the nozzles for letting well fluid into the tool, aflow hindering element arranged on an outside of the housing dividingthe tool in a first and a second tool part and dividing the casing in afirst and a second casing part and a rotatable shaft connecting thenozzle head with the housing. Furthermore, the invention relates to awireline cleaning tool and to a cleaning method.

BACKGROUND ART

During oil production, the completion needs to be optimised in order toproduce as much oil as possible. Therefore, it is necessary that somevalves are open and others closed. However, such valves may get stuckdue to precipitation of scales and other particles accumulated on thevalve so that the valve is blocked. Thus, it is sometimes necessary toclean the valves before they can be operated.

Known cleaning tools require the presence of coiled tubing on the rig orvessel in order to clean a valve in a casing within a wellbore. However,such coiled tubing is not always situated on the rig or vessel andtherefore needs to be transported to the rig or vessel.

SUMMARY OF THE INVENTION

It is an object of the present invention to wholly or partly overcomethe above disadvantages and drawbacks of the prior art. Morespecifically, it is an object to provide a downhole cleaning systemwhich is more simple and easier to submerge into a wellbore withoutusing drill pipes or coiled tubing.

The above objects, together with numerous other objects, advantages, andfeatures, which will become evident from the below description, areaccomplished by a solution in accordance with the present invention by adownhole cleaning system for cleaning an element inside a casing in awellbore comprising well fluid having a wellbore pressure, comprising:

the casing,

a wireline cleaning tool having a longitudinal direction and comprising:

-   -   a rotatable nozzle head having a plurality of nozzles,    -   a tool housing having an inlet being in fluid communication with        the nozzles for letting well fluid into the tool,    -   a flow hindering element arranged on an outside of the housing        dividing the tool in a first and a second tool part and dividing        the casing in a first and a second casing part, and    -   a rotatable shaft connecting the nozzle head with the housing,

-   wherein the system further comprises a pumping device for    pressurising the well fluid in the first part of the casing to a    pressure substantially above the wellbore pressure and above a    pressure in the second part of the casing so that well fluid is    pumped in through the inlet and out through the nozzles.

In an embodiment, the nozzle head may have a side face facing an innerface of the casing, and the nozzles of the nozzle head may be arrangedalong the side face.

By having the nozzles in the side face, the nozzles are arranged closerto the object to be cleaned e.g. a gas lift valve (GLV) arranged in aside pocket of the casing than if arranged in front of the tool.

Also, part of the nozzles may form part of the side face.

Moreover, the nozzle head may have a circumference and the nozzles maybe arranged along the circumference facing the inner face of the casing.

Further, the nozzles may be arranged in rows along the side face.

Arranging the nozzles in rows expands the range of the ejecting area inthe longitudinal direction of the tool. In order to clean an object e.g.a GLV, the nozzle head has to be moved in the longitudinal direction,and by having rows of nozzles the nozzle head does not have to be movedfor a distance as long as when having only one row of nozzles or onlyone nozzle nor as many times as a head having only one row.

Additionally, each nozzle may eject the fluid in one beam being afocused beam.

Ejecting fluid through the nozzle in a beam is more efficient forremoving scales and other solid elements fastened to the wall of thecasing or a GLV than more diffused droplets which is to a greater extentused for just washing or flushing the object to be cleaned.

Each nozzle may be arranged in an angle in relation to a longitudinalextension of the tool.

In an embodiment, the nozzles may be arranged in a predetermined patternalong the side face of the nozzle head.

The pattern is determined by the pressure in the well at the location ofthe object or area of the casing to be cleaned and the pressureavailable in the fluid to be ejected through the nozzles, so that thepower of the pump is used in the most optimal manner. Hereby, it isensured that the nozzles are not arranged too close to each other andhence that the beam of fluid ejected through one nozzle does not mergewith a beam of an adjacent nozzle, thereby reducing its cleaning effect.

Moreover, the nozzles may be fixedly arranged in the nozzle head.

Furthermore, the nozzles may be arranged spaced apart along thecircumference.

Also, the downhole cleaning system according to the invention maycomprise a control device to control the rotation of the shaft and thenozzle head.

In an embodiment, the downhole cleaning system may comprise a controldevice for controlling a rotational speed of the nozzle head or whichnozzle/nozzles is/are allowed to eject fluid.

By having a control device, the nozzle/nozzles is/are hindered from freerotation as known from prior art tools where some nozzles are designedto rotate as the pressurised fluid is forced through them. Hereby,substantially all energy of the pressurised fluid is used only forrotation of the nozzle and not for providing a beam of pressurised fluidejected through the nozzles.

Moreover, the control device may be a hydraulic control unit arranged inthe tool for controlling which nozzles are open and which nozzles areclosed.

In one embodiment, the control device may be an electrical motor forrotating the shaft.

In another embodiment, the control device may comprise a gear, a motorbrake or a centrifugal brake.

Also, the control device may be a hydraulic control unit arranged in thetool for controlling which nozzles are open and which nozzles areclosed.

Furthermore, the nozzle head may comprise a hydraulic control unit forcontrolling which nozzles are open and which nozzles are closed.

By having a hydraulic control unit for controlling which nozzles areejecting fluid, the nozzles not facing the object to be cleaned are notejecting fluid and all pressure in the fluid is used for ejecting fluidthrough the nozzle or nozzles facing the object to be cleaned. Thus, noenergy of the pressurised fluid is lost in nozzles not facing the objectto be cleaned and/or no energy is used for rotating the nozzle head.Furthermore, by controlling which nozzle/nozzles is/are allowed to ejectfluid, only one or a few of the nozzles is/are ejecting fluid and thepressure of the fluid ejected from that or these nozzles issignificantly larger than if ejected through all the nozzles at the sametime even if the object is extending along the whole circumference ofthe casing. In this way, each nozzle is able to clean harder materialssuch as scales than what is possible in prior art tools in which mostenergy in the pressure fluid is used for rotating the nozzles.

In addition, the nozzle head may comprise a hydraulic control unit forcontrolling a supply of fluid to each nozzle.

In one embodiment, the shaft may be hollow for supplying the well fluidto the nozzle head.

In another embodiment, the flow hindering element may be a packer, aninflatable unit, a rubber element or an elastomeric element

The downhole cleaning system according to the invention may furthercomprise a stroker being a device providing a stroking reciprocatingmovement of the nozzle head in relation to the longitudinal direction ofthe tool, or a piston interacting with a piston housing in which aspring device is arranged for providing a reciprocating movement of thenozzle head in relation to the longitudinal direction of the tool.

In one embodiment, the tool may comprise anchoring units.

In another embodiment, a filter may be arranged upstream of the inlet orinside the inlet.

Furthermore, the downhole cleaning system may comprise a downholedriving unit driving the tool and itself in the casing.

Also, the downhole cleaning system may comprise a measuring devicemeasuring a rotational speed of the nozzle head.

Additionally, the downhole cleaning system may comprise a control unitto control the measuring device from surface.

In one embodiment, the nozzle head may comprise a check valve.

Moreover, the well fluid being pressurised may be the fluid being in thefirst part.

Further, the well fluid may be pressurised when being in the first partof the casing.

The well fluid may be taken from the first part for being pressurised.

Furthermore, the pumping device may pump the fluid out through thenozzles.

The present invention also relates to a wireline cleaning tool arrangedin a casing downhole and having a longitudinal direction, comprising:

-   -   a rotatable nozzle head having a plurality of nozzles,    -   a tool housing having an inlet being in fluid communication with        the nozzles for letting well fluid into the tool and out through        the nozzles,    -   a flow hindering element arranged on an outside of the housing        dividing the tool in a first and a second tool part and dividing        the casing in a first and a second casing part, and    -   a rotatable shaft connecting the nozzle head with the housing,

-   wherein the shaft may be a hollow shaft for supplying the nozzles    with well fluid.

Said wireline cleaning tool may further comprise a wireline connectorconnected with the tool housing for connecting the tool with a wireline.

The tool may further comprise a pumping device for pressurising the wellfluid in the first part of casing to a pressure substantially above thewellbore pressure and above a pressure in the second part of the casingso that well fluid is pumped in through the inlet and out through thenozzles.

Also, the wireline cleaning tool as described above may comprise acontrol device for controlling a rotational speed of the nozzle head orwhich nozzle/nozzles is/are allowed to eject fluid.

Moreover, the control device may be a hydraulic control unit arranged inthe tool for controlling which nozzles are open and which nozzles areclosed.

The tool may further comprise a control device to control the rotationof the shaft and the nozzle head.

Also, the tool may further comprise a control device for controlling arotational speed of the nozzle head.

Said control device may be an electrical motor for rotating the shaft.

Further, the control device may comprise a gear, a motor brake or acentrifugal brake.

Additionally, the tool may further comprise a stroker being a deviceproviding a stroking reciprocating movement of the nozzle head inrelation to the longitudinal direction of the tool, or a pistoninteracting with a piston housing in which a spring device is arrangedfor providing a reciprocating movement of the nozzle head along thelongitudinal direction of the tool housing.

The tool may further comprise a measuring device measuring a rotationalspeed of the nozzle head.

Finally, the invention relates to a cleaning method comprising the stepsof entering a cleaning tool of the system according to the inventioninto a casing, activating the pumping device and pressurising the firstcasing part, turning the nozzle head and cleaning a casing element byletting well fluid in through the inlet in the pressurised first casingpart and out through nozzles in the second casing part.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its many advantages will be described in furtherdetail below with reference to the accompanying schematic drawings,which for the purpose of illustration show some non-limiting embodimentsand in which

FIG. 1 shows a downhole cleaning system in a casing,

FIG. 2 shows a partly cross-sectional view along the longitudinaldirection of the downhole cleaning system seen from the side,

FIG. 3 shows a partly cross-sectional view of another embodiment of thesystem, and

FIG. 4 shows another embodiment of the downhole cleaning system in acasing.

All the figures are highly schematic and not necessarily to scale, andthey show only those parts which are necessary in order to elucidate theinvention, other parts being omitted or merely suggested.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a downhole cleaning system 1 for cleaning an element 2,such as a gas lift valve (GLV), a sleeve or a side pocket mandrel, in acasing 3 in a wellbore 4 comprising well fluid 5 having a well fluidpressure Pw. The downhole cleaning system 1 comprises the casing 3 and awireline cleaning tool 10. The wireline cleaning tool 10 has alongitudinal direction 11, and comprises in the end furthest away fromthe surface a rotatable nozzle head 12 having a plurality of nozzles 13for cleaning the gas lift valve by jetting high pressurised well fluidout through the nozzles towards the valve.

By having a cleaning tool or a wireline cleaning tool 10, the cleaningoperation can be performed anywhere in the well, also in the morehorizontal parts of the well. No landing nipple is required in order toperform a cleaning operation. The system is easy to use and the cleaningtool easily retrieved from the well by pulling in the wireline.

The wireline cleaning tool 10 has a tool housing 14 having an inlet 15for letting well fluid into the tool 10 and the inlet 15 is inside thetool in fluid communication with the nozzles 13. The well fluid travelsin through the inlet and out through the nozzle head, illustrated witharrows. The wireline cleaning tool 10 is submerged into the casing 3 inthe well and a flow hindering element 16 arranged on an outside 17 ofthe housing 14 is set or inflated so that it divides the casing 3 in afirst 20 and a second casing part 21. This enables that the well fluidin the first casing part 21 can be pressurised from the top of the wellby a pumping device 23 and the fluid is forced into the inlets 15 andout through the nozzles in order to clean the casing or elementstherein. Thus, the second part of the casing 21 has a substantiallylower well fluid pressure so that the high pressurised well fluid in thefirst part 20 can be ejected as jets or beams in the well fluid in thesecond part of the casing. In this way, the casing is used as the coiledtubing or drill pipe in order to provide the nozzles with highpressurised fluid; however, the fluid jetted from the nozzles is not aspecial cleaning fluid but merely the well fluid surrounding the tool.Thus, the environment surrounding the gas lift valve to be cleaned isnot interfered.

As shown in FIG. 1, the wireline cleaning tool 10 is connected with awireline 41. The tool comprises an electronic section 30, a motor 31, apump 32 and an anchoring device 33 in a first tool part 18 above theflow hindering element 16. In a second tool part 19 below the flowhindering element 16, the nozzle head 12 is arranged. In anotherembodiment, the cleaning tool could have a battery pack, and thus thewireline can be dispensed with if needed, and the tool could flowupwards with the flow when the hindering element was somewhat deflatedor released from the casing and thus the hindering element serves as aparachute.

In FIG. 2, the tool 10 is shown having a rotatable shaft 22 connectingthe nozzle head 12 with the housing 14. The rotation of the shaft iscontrolled by a control device 24 in the form of an electrical motorhaving a gear, a motor brake or a centrifugal brake 25. The shaft 22 ishollow and in fluid communication with the inlet 15 for supplying wellfluid to the nozzles 13 of the nozzle head 12. The shaft 22 is connectedwith the motor control device 24 which controls the rotation of thenozzle head 12 while fluid is jetted out through the nozzles 13. If thenozzle head was not controlled, the well fluid jet stream or beam 43ejected from the nozzles would lose its effect as fluid ejected throughthe nozzles would then force the nozzle head to rotate too fastresulting in the jet stream being spread along an inner circumference ofthe casing and not ejected as a straight line in the radial direction ofthe casing. Hereby, substantially all energy of the pressurised fluid isused for rotation of the nozzle and not for providing a beam ofpressurised fluid ejected through the nozzles.

The flow hindering element 16 is shown as a rubber element beingsqueezed in the longitudinal direction 11 of the tool between two rings42 forcing the rubber element radially outwards to seal against thecasing at a pressure of 3000-5000 PSI. The flow hindering element couldalso be a packer, an inflatable unit or an elastomeric element. The flowhindering element does not necessarily have to seal against the innerwall of the casing in order to be able to create a pressure differencebetween the first and upper part of the casing and the second and lowerpart of the casing.

The tool 10 is anchored up inside the casing 3 by means of anchoringunits 35 so that the nozzle head 12 is arranged outside a target area tobe cleaned. The flow hindering element 16 is then inflated or set, andthe pumping device 23 pressurising the well fluid in the first and toppart of the casing 20 is activated. High pressurised fluid issubsequently jetted as a jet stream out through the nozzles 13 of thenozzle head 12 as the nozzle head turns in a controlled manner so thatthe jet streams do not loose too much jetting power. In someembodiments, the tool has only a hindering element which is sufficientto hold the tool in the intended position opposite the object or thearea of the casing to be cleaned.

The nozzle head comprises a hydraulic control unit 34 for controllingwhich of the nozzles is allowed to emit or jet fluid to clean a valve orsimilar element. The hydraulic control unit 34 controls the openings andclosings of the nozzles and/or the supply of fluid to each nozzle. Ascan be seen in FIG. 1, only two of the nozzles jet fluid into the casingin order to clean an element, such as a valve. In FIG. 2, only onenozzle jets fluid. If a high fluid velocity is needed in order to cleanan object free of e.g. hard scales, the hydraulic control unit only letsone nozzle jet at a time. However, if a high volume of fluid is needed,the hydraulic control unit lets several nozzles jet. Furthermore, thehydraulic control unit has means to control in which angles along thecircumference of the nozzle head the nozzles are to jet so that theirjets hit the element which is to be cleaned.

The nozzle head has an end face 51 and a side face 50, and the nozzlesare arranged in a predetermined pattern 52 along the side face of thenozzle head. The nozzles are arranged in rows 53 along the circumference54 of the nozzle head having a mutual distance along the circumference.The pattern is determined by the pressure available in the fluid to beejected through the nozzles and the pressure in the second part of thewell at the location of the object or area of the casing to be cleanedand so that the power of the pump is used in the most optimal manner.The predetermined pattern is to ensure that the nozzles are not arrangedtoo close to each other hence ensuring that the beam of fluid ejectedthrough one nozzle does not merge with a beam or jet of an adjacentnozzle, thereby reducing the cleaning effect of each beam or jet. Thenozzles may be fixedly arranged in the nozzle head ensuring that energyof the pressurised fluid is used for providing a jet or beam out throughthe nozzles at the most optimal angle of attack in relation to thescales type or the type of the undesired element to be removed from theobject to be cleaned. The nozzles are designed to eject a focused beamat a predetermined angle to provide needle punching effect or a wedgingeffect to crack the material to be removed.

In order to reach a larger target area, the tool may have means formoving the nozzle head in a reciprocating movement. In FIG. 2, a piston26 interacting with a piston housing 27 in which a spring device 28 isarranged provides a reciprocating movement of the nozzle head 12 inrelation to the longitudinal direction 11 of the tool 10. In FIG. 3, thetool 10 comprises a stroker 29 being a device providing a strokingreciprocating movement of the nozzle head 12 in relation to thelongitudinal direction 11 of the tool 10. The reciprocating movement ofthe nozzle head 12 is illustrated by a double arrow in FIG. 3.

In another embodiment, the control device is a hydraulic control unitcomprising the shaft having grooves in the form of channels extending inthe longitudinal direction and the outer surface of the shaft and thefluid supplied to the nozzles flows in the channels. The shaft isrotated so that some channels are opposite some nozzles which in thisway is allowed to eject fluid, and when the shaft is rotated again, thechannels are arranged opposite other nozzles which will then be the nextto be allowed to eject a beam of pressurised fluid. In this way, theshaft is rotated to control which nozzle is allowed to eject fluid.

The wireline cleaning tool comprises a filter 36 arranged upstream ofthe inlet 15 or in the inlet. In FIG. 2, the filter 36 or screensurrounds the part of the tool 10 having the inlet 15. The tool 10comprises several inlets, all in fluid communication with the hollowshaft. The hollow shaft may be internally sectionised having an internalframe structure to strengthen the shaft.

As shown in FIG. 4, the downhole cleaning system 1 may further comprisea downhole driving unit 37 driving the tool 10 and itself forward in thecasing 3. The driving unit 37 has wheels on arms and can be used as theanchoring device in order to set the packer. The downhole cleaningsystem 1 may also comprise a measuring device 38 measuring a rotationalspeed of the nozzle head 12. As shown in FIG. 4, the measuring device 38may be arranged in the motor control device 24 around the shaft 22 sothat the nozzle head is controlled to rotate at a speed lower than 30RPM, preferably lower than 25 RPM and more preferably lower than 20 RPM.The control device 24 may be controlled from above surface by means of acontrol unit 39 shown in FIG. 4.

Before and after the cleaning operation, a logging unit of the cleaningtool can investigate the casing to see which part or element of thecasing needs to be cleaned and if the element to be cleaned is properlycleaned.

The nozzle head 12 may further comprise a check valve 40 in an endopposite the end connected with the shaft 22.

The tool 10 may comprise a chamber with a cleaning fluid which is mixedwith the well fluid before being jetted out through the nozzles 13.

By fluid or well fluid is meant any kind of fluid which may be presentin oil or gas wells downhole, such as natural gas, oil, oil mud, crudeoil, water, etc. By gas is meant any kind of gas composition present ina well, completion, or open hole, and by oil is meant any kind of oilcomposition, such as crude oil, an oil-containing fluid, etc. Gas, oil,and water fluids may thus all comprise other elements or substances thangas, oil, and/or water, respectively.

By high pressurised fluid is meant fluid flowing at a volume flow rateof at least 250 L/min, preferably at least 300 L/min and even morepreferably 350 L/min.

By a casing is meant any kind of pipe, tubing, tubular, liner, stringetc. used downhole in relation to oil or natural gas production.

In the event that the system is not submerged all the way into thecasing, a downhole tractor can be used to push the system all the wayinto position in the well. A downhole tractor is any kind of drivingtool capable of pushing or pulling tools in a well downhole, such as aWell Tractor®.

Although the invention has been described in the above in connectionwith preferred embodiments of the invention, it will be evident for aperson skilled in the art that several modifications are conceivablewithout departing from the invention as defined by the following claims.

1.-28. (canceled)
 29. A wireline cleaning tool (10) arranged in a casingdownhole and having a longitudinal direction (11), comprising: arotatable nozzle head (12) having a plurality of nozzles (13), a toolhousing (14) having an inlet (15) being in fluid communication with thenozzles for letting well fluid into the tool and out through thenozzles, a flow hindering element (16) arranged on an outside (17) ofthe housing dividing the tool in a first (18) and a second (19) toolpart and dividing the casing in a first (20) and a second (21) casingpart, and a rotatable shaft (22) connecting the nozzle head with thehousing, the shaft being a hollow shaft for supplying the nozzles withwell fluid, wherein the wireline cleaning tool further comprises acontrol device for controlling a rotational speed of the nozzle head.30. A wireline cleaning tool according to claim 29, wherein the toolfurther comprises a pumping device (32) for pressurising the well fluidin the first part of casing to a pressure substantially above thewellbore pressure and above a pressure in the second part of the casingso that well fluid is pumped in through the inlet and out through thenozzles.
 31. A wireline cleaning tool according to claim 29, wherein thecontrol device is also configured for controlling which nozzle/nozzlesis/are allowed to eject fluid.
 32. A wireline cleaning tool according toclaim 31, wherein the control device is a hydraulic control unitarranged in the tool for controlling which nozzles are open and whichnozzles are closed.
 33. A downhole cleaning system (1) for cleaning anelement (2) inside a casing (3) in a wellbore (4) comprising well fluid(5) having a wellbore pressure (Pw), comprising: the casing, and awireline cleaning tool (10) according to claim 29, wherein the systemfurther comprises a pumping device (23) for pressurising the well fluidin the first part of the casing to a pressure substantially above thewellbore pressure and above a pressure in the second part of the casingso that well fluid is pumped in through the inlet and out through thenozzles, wherein the system further comprises a control device (24) forcontrolling a rotational speed of the nozzle head.
 34. A downholecleaning system according to claim 33, wherein the control device (24)is also configured for controlling which nozzle/nozzles is/are allowedto eject fluid.
 35. A downhole cleaning system according to claim 33,wherein the control device is a hydraulic control unit (34) arranged inthe tool for controlling which nozzles are open and which nozzles areclosed.
 36. A downhole cleaning system according to claim 33, furthercomprising a control device (24) to control the rotation of the shaftand the nozzle head.
 37. A downhole cleaning system according to claim33, wherein the control device is an electrical motor for rotating theshaft.
 38. A downhole cleaning system according to claim 33, wherein thecontrol device comprises a gear, a motor brake or a centrifugal brake(25).
 39. A downhole cleaning system according to claim 33, wherein thenozzles are fixedly arranged in the nozzle head.
 40. A downhole cleaningsystem according to claim 33, wherein the shaft is hollow for supplyingthe well fluid to the nozzle head.
 41. A downhole cleaning systemaccording to 33, wherein the flow hindering element is a packer, aninflatable unit, a rubber element or an elastomeric element.
 42. Adownhole cleaning system according to claim 33, further comprising astroker (29) being a device providing a stroking reciprocating movementof the nozzle head in relation to the longitudinal direction of thetool, or a piston (26) interacting with a piston housing (27) in which aspring device (28) is arranged for providing a reciprocating movement ofthe nozzle head in relation to the longitudinal direction of the tool.43. A downhole cleaning system according to claim 33, wherein a filter(36) is arranged upstream of the inlet or inside the inlet.
 44. Adownhole cleaning system according to claim 33, further comprising adownhole driving unit (37) driving the tool and itself in the casing.45. A downhole cleaning system according to 33, further comprising ameasuring device (38) measuring a rotational speed of the nozzle head.46. A downhole cleaning system according to claim 45, further comprisinga control unit (39) to control the measuring device from surface.
 47. Adownhole cleaning system according to 33, wherein the nozzle headcomprises a check valve (40).
 48. A cleaning method comprising the stepsof: entering a cleaning tool according to 29 into a casing, activatingthe pumping device and pressurising the first casing part, turning thenozzle head, and cleaning a casing element by letting well fluid inthrough the inlet in the pressurised first casing part and out throughnozzles in the second casing part.